Power supply device for vehicle

ABSTRACT

A vehicle power supply device converts power from high voltage to low voltage by selectively connecting a predetermined power storage element group to a low voltage electric load from a high voltage power supply formed by connecting power storage elements in series. A leakage current from the high voltage power supply is measured during the dead time period when the power storage element group is not connected to the low voltage electric load. When the value exceeds a predetermined value, the connection between the power storage element group and the low-voltage electric load is interrupted, so that electric shock is prevented.

TECHNICAL FIELD

The present invention relates to a power supply device mounted on avehicle. The power supply device includes a high-voltage power storagemeans particularly used for vehicle traveling and the like, and alow-voltage power supply for supplying an electric load other than thatfor a vehicle traveling. The power supply device is configured to obtainthe low voltage power supply from the high-voltage power storage meansvia a step-down means.

BACKGROUND ART

As the power supply device, a vehicle power supply device according tothe proposal of the present applicant is known (Patent Publication (1)).In this vehicle power supply device, the high voltage power supply isformed by connecting power storage elements in series. The vehicle powersupply device performs power conversion from a high voltage to a lowvoltage by selectively connecting a predetermined power storage elementgroup to a low voltage electric load. The vehicle power supply deviceswitches the power storage element group at high speed to make theswitching loss of the switching means almost zero.

PRIOR ART PUBLICATION Patent Publication [Patent Publication (1)]Japanese Laid-Open Patent Publication No. 2018-26973 SUMMARY OF THEINVENTION Problem(s) to be Solved by the Invention

There are various embodiments of the electric power storage means fordriving the vehicle from a low voltage of about 48 V to a system using ahigh voltage of about 600 V. Generally, a vehicle using a voltageexceeding 60 V is provided with a configuration for preventing anelectric shock accident. This prevents an electric shock accident whenthe human body touches the electric circuit portion connected to thepower storage means of the vehicle.

Therefore, in a general high voltage system of a vehicle, a DC-DCconverter provided with an isolation transformer is arranged between thehigh voltage part and the low voltage part as shown in FIG. 1 . At thesame time, the high voltage circuit floats both the negative potentialcircuit and the positive potential circuit while avoiding directconnection with the vehicle body. With this configuration, even if thehuman body touches any part of the circuit portion including the highvoltage power storage means, no electric shock is caused.

Here, according to Patent Publication (1), the low potential side of theload means 50, which is a low voltage circuit, is generally connected tothe vehicle body as a body ground of a 12V power supply. When any one ormore of the switch means (30 to 35) is closed, any of the connectionpoints of the power storage means (20 a to 20L) connected in series onthe high voltage side is directly connected to the vehicle body.Therefore, if the human body touches the high voltage circuit, anelectric shock will occur. Specifically, it is assumed that the totalseries voltage of the power storage means (20 a to 20L) is 480V. Whenthe human body touches the positive potential side of the power storagemeans 20 a and the vehicle body at the moment when the switch means 35is closed, a high voltage of 480 V is applied to the human body. It ispossible that an electric shock accident may occur.

The present invention has been made in view of the above problems. Thiscan be applied to a case where a vehicle power supply device mounted ona vehicle and obtaining a low voltage power supply from a high voltagepower supply via a step-down means is configured as a system having avoltage exceeding 60 V on the high voltage power supply side. 60V is thevoltage of the electric shock limit of the human body. Even in thiscase, it is possible to prevent an electric shock accident without usingan insulating means such as a transformer. Further, the presentinvention provides a power supply device for a vehicle that easilyobtains a power conversion efficiency of about 100% in a powerconversion function to the low voltage side.

Solution(s) to the Problem(s)

The present invention described in claim 1 is a power supply device forvehicle, comprising: an electric load that operates at a predeterminedlow voltage; a high-voltage power supply that obtains a high-voltage DCpower supply by connecting in series a plurality of power storageelements constituting each node that supplies said predetermined lowvoltage; a high-voltage load device connected to the high-voltage powersupply via a wire harness; a plurality of switch means providedcorresponding to each node that supplies the predetermined low voltageto the electric load; a control means, wherein the control meanssupplies a voltage by turning on the switch means for supplying avoltage from at least one node and turning off the switch means forsupplying a voltage from another node, after setting a dead time periodto turn off all switch means once, by sequentially repeating the controlof turning on the switch means of the node that supplies the voltagenext and turning off the switch means that supplies the voltage from theother node, the voltage is supplied from all the storage elements; acutoff means for cutting off an electric circuit between thehigh-voltage power supply and the high-voltage load device; and aleakage detection means that detects a leakage current between the highvoltage power supply and a ground potential and sends a signal to saidcontrol means, wherein the control means determines the signaltransmitted from the leakage detection means during the dead time periodwhen the plurality of switching means are all off, and when the leakagecurrent is equal to or higher than a predetermined current, the cutoffmeans are kept off for a predetermined period of time.

The present invention described in claim 2 is a power supply device fora vehicle, wherein in said high voltage power supply, a plurality ofpower storage elements constituting the node of which n (n: naturalnumber) pieces make up the predetermined low voltage are connected inseries (n×N (N: natural number)), and DC power source having a highvoltage N times the predetermined low voltage can be obtained.

The present invention described in claim 3 is a power supply device fora vehicle, wherein said control means controls the switch means so as toperiodically change a plurality of selected nodes.

The present invention described in claim 4 is a power supply device fora vehicle, wherein said control means determines a node to be selectedso that the charge/discharge states of the plurality of power storageelements become substantially uniform.

The present invention described in claim 5 is a power supply device fora vehicle, wherein said control means determines a selective holdingtime of each node so that the charge/discharge states of the pluralityof power storage elements become substantially uniform.

The present invention described in claim 6 is a power supply device fora vehicle, wherein a time connecting any of node to said electric loadby said switch means is set so as to a time during which the leakagecurrent flowing from the high voltage power supply to the human body tobe less than a time during which causes an electric shock accident inthe human body.

The present invention described in claim 7 is a power supply device fora vehicle, wherein said time connecting any of node to said electricload by said switch means is set so as to a time during which inverselyproportional to the voltage value of the high voltage power supply, or atime during which inversely proportional to the current value detectedby the leakage detecting means.

The present invention described in claim 8 is a power supply device fora vehicle, wherein said control means fixes the cutoff means to an offstate when the leakage detection value of said leakage detection meansis equal to or higher than a predetermined current value.

The present invention described in claim 9 is a power supply device fora vehicle, wherein said control means holds a state in which the cutoffmeans are off for a predetermined time when the leakage detection valueof the leakage detection means is equal to or higher than apredetermined current value, and after that, again repeats the operationin which the cutoff means are on.

The present invention described in claim 10 is a power supply device fora vehicle, wherein said control means controls said switching means soas to a product of a period in which each node and the electric load areconnected and the leakage detection value of the leakage detection meansis 0.003 amperes×1 second or less.

The present invention described in claim 11 is a power supply device fora vehicle, wherein said control means sets a cycle for switching a nodeselected by said switching means to a predetermined value or less sothat a magnitude of a charge/discharge depth in each node of the powerstorage element is equal to or less than a predetermined value.

The present invention described in claim 12 is a power supply device fora vehicle, wherein a capacitor is connected in parallel with theelectric load.

The present invention described in claim 13 is a power supply device fora vehicle, wherein said dead time period or a capacitance value of thecapacitor is set so that a voltage drop width applied to the electricload during the dead time period is not more than a predetermined value.

The present invention described in claim 14 is a power supply device fora vehicle, wherein the capacitor is arranged in parallel with each nodeof said power storage element.

The present invention described in claim 15 is a power supply device fora vehicle, wherein from each node of the high-voltage power source thatobtains a high-voltage DC power supply by connecting in series aplurality of power storage elements, AC power is supplied to theelectric load by alternately reversing the polarity with a potentialside and a lower side at predetermined periods when the electric load isconnected by the switching means.

Effect(s) of the Invention

The vehicle power supply device described in claim 1, Claim2, assumingthat the voltage of the low voltage power supply is [VL], the voltage[VH] of the high voltage power supply to which the power storageelements are connected in series is VL×N (N is a natural number).Moreover, since the number of the power storage elements is N×n (n is anatural number), for example, when [VL] is 12V and N=40, [VH] is 480V.Assuming that n=4, a high voltage power supply is composed of a total ofN× n=160 power storage elements in series. The voltage of each powerstorage element is 3V.

Therefore, in order to obtain a low voltage power supply of 12V, fourpower storage elements connected in series may be selected in a groupmanner and connected to an electric load.

However, in order to obtain a 12V low voltage power supply from a 480Vhigh voltage power supply, it is not necessary to use a DC-DC converterusing a known switching power supply circuit or the like. Step-down canbe realized by a simple switching means that selectively connects to anelectric load from each node (group node) of the power storage elementconnected in series.

Therefore, the configuration of the switching means can be simplified.Since the known switching loss and the loss generated from the inductorcan be significantly reduced, the power loss for step-down can bereduced and the heat dissipation structure can be simplified. As aresult, the weight and cost of the power supply device including thedevice for such step-down can be reduced.

Here, a part of the nodes of the power storage element connected inseries of the high voltage power supply is connected to the low voltagecircuit, that is, the metal part of the vehicle body via the switchingmeans. When a human touches the high voltage power supply circuit part,an electric shock current flows through the human body.

However, the control means detects the current flowing from the highvoltage power supply through the human body as the measured currentvalue of the leakage detection means during the dead time period whenall the switching means are turned off. When the value is equal to orhigher than a predetermined value, the cutoff means for disconnectingthe electric circuit connected to the high voltage load device from thevehicle power supply device via the wire harness connected to theoutside is held in the off state, an electric shock accident can beprevented.

The vehicle power supply device described in claim 2, in the highvoltage power supply, a plurality of power storage elements constitutinga node having a predetermined low voltage with n (n: natural number) areconnected in series (n×N (N: natural number)). A DC power supply havinga high voltage N times a predetermined low voltage is obtained.Therefore, it is possible to efficiently supply a high voltage and apredetermined low voltage by using all the power storage elements.

The vehicle power supply device described in claim 3, the control meansperiodically changes the node selected by the switching means from theplurality of power storage elements. Among the power storage elementsconnected in series, it is possible to prevent a problem that only apart of the power storage elements is discharged and the other powerstorage elements are overcharged.

The vehicle power supply device described in claim 4, the control meansdetermines the node to be selected so that the charge/discharge statesof the plurality of power storage elements are substantially uniform. Italso has a known cell balance function required when charging anddischarging a plurality of power storage elements in series.

The vehicle power supply device described in claim 5, the control meansdetermines the selective holding time of each node so that thecharge/discharge states of the plurality of power storage elementsbecome substantially uniform. The selective holding time of each node isdetermined so that the charge/discharge state of the plurality of powerstorage elements becomes substantially uniform and the discharge time islong for the node selected from the power storage elements having alarge charge amount. On the contrary, the selective holding time of eachnode is determined so that the discharge time is short for the nodeselected from the power storage elements having a small charge amount.It also has a known cell balance function required when charging anddischarging a plurality of power storage elements in series.

It is said that when a high voltage is applied to the human body, thereis no effect on the human body if the current value is 5 mA or less. Itis known that in a current range larger than this, the human bodyreaction changes depending on the duration. As the current valueincreases, the human body is damaged by electric shock in a short time.

Therefore, in the earth-leakage circuit breaker used for a generalcommercial power supply, the earth-leakage detection sensitivity of 30mA×0.1 sec is set.

The vehicle power supply device described in claim 6, the control meanssets the period for connecting each node to the low-voltage electricload by the switching means to be less than the time during which anelectric shock accident occurs in the human body. This period is theduration of the leakage current flowing from the high voltage powersupply to the human body. Even when a person touches a circuit part of ahigh voltage power supply, it is possible to eliminate the damage to thehuman body.

The vehicle power supply device described in claim 7, the control meansis set so that the period for connecting each node and the electric loadby the switching means is a duration inversely proportional to thevoltage value of the high voltage power supply. Alternatively, theduration is set to be inversely proportional to the leakage currentvalue to the human body. When the voltage value of the high voltagepower supply or the leakage current value to the human body is high andthe electric shock current of the human body is large, the energizationtime to the human body, that is, the electric shock time can beshortened, so that the safety is further improved.

The vehicle power supply device described in claim 8, the control meansfixes the cutoff means to the OFF state when the leakage detection valueof the leakage detection means is equal to or higher than apredetermined current value. When a leakage from a high voltage powersupply is detected, the high voltage power supply continues to floatfrom the vehicle body, so that safety is further improved.

The vehicle power supply device described in claim 9, the control meansholds a state in which the cutoff means are OFF for a predetermined timesuch as 0.5 seconds when the leakage detection value of the leakagedetection means is equal to or higher than a predetermined currentvalue. After that, the cutoff means repeats the operation of turning ON.Ensure safety by giving a sufficient pause time to the electric shockcurrent to the human body. Even if a temporary leakage current occursdue to a failure of each part of the power supply device of the vehiclebody, the power supply from the high voltage power supply to the highvoltage load device is resumed, so that the vehicle function can bemaintained.

The vehicle power supply device described in claim 10, the control meanscontrols the switching means so that the product of the period forconnecting each node and the electric load and the leakage detectionvalue of the leakage detection means is 0.003 amperes×1 second or less.It is possible to secure the same level of safety as the standard 0.03amps×0.1 seconds or less of the earth-leakage circuit breaker used ingeneral commercial power supplies.

The vehicle power supply device described in claim 11, the control meanssets a cycle for switching the node selected by the switching means sothat the magnitude of the charge/discharge depth at each node of thepower storage element is equal to or less than a predetermined value. Itis possible to minimize the decrease in the life of each power storageelement due to the charging/discharging depth of each power storageelement being too large.

The vehicle power supply device described in Claim 12, the control meanspowers the switching means from the capacitor during a so-called deadtime period that disconnects the connection between all the nodes andthe electrical load. As a result, it is possible to prevent the voltagesupplied to the electric load from dropping. The voltage supplied to theelectric load can be kept stable.

The vehicle power supply device described in Claim 13, since the voltageapplied to the electric load before and after the switching means isswitched can be maintained, the potential difference between both endsof the switching means immediately before the switching means is turnedon can be eliminated, and the switching loss can be eliminated.

Next, if the internal resistance of the power storage element is largeimmediately after the switching means switches the connection to anarbitrary node, it takes a lot of time to charge the capacitor connectedin parallel with the electric load. Therefore, it is inevitable that thevoltage supplied to the electric load will drop at the timing when theswitching means is switched.

The vehicle power supply device described in claim 14, a capacitor witha small internal impedance is placed in parallel with the series node ofthe power storage element. Immediately after the switching meansswitches the connection to any node, the capacitor can be charged with asufficiently small power supply impedance, that is, a large current. Itis possible to suppress a decrease in the voltage supplied to theelectric load.

The vehicle power supply device described in claim 15, power is suppliedfrom each node of a high voltage power supply that obtains ahigh-voltage DC power supply by connecting a plurality of power storageelements in series. The polarities of the high-potential side and thelow-potential side when connected to the electric load by the switchingmeans are alternately reversed at predetermined intervals. AC power issupplied to the electric load. AC power can be supplied from the vehiclefor the use of household appliances that require commercial power.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a diagram showing a basic configuration of a general vehiclepower supply device;

FIG. 2 a diagram showing a basic configuration of a vehicle power supplydevice according to an embodiment of the present invention;

FIG. 3 a timing chart showing the basic operation of the vehicle powersupply device according to the embodiment of the present invention;

FIG. 4 a diagram illustrating leakage detection of a vehicle powersupply device according to the embodiment of the present invention;

FIG. 5 a diagram showing a configuration for measuring the voltage ofeach node of the power storage element;

FIG. 6 a diagram showing the selective holding time of each node;

FIG. 7 a diagram showing an embodiment of a vehicle power supply deviceaccording to the embodiment of the present invention;

FIG. 8 a diagram illustrating power loss of a switching element;

FIG. 9 a diagram illustrating power loss of a switching element;

FIG. 10 a diagram illustrating the charge/discharge depth of the powerstorage element;

FIG. 11 a diagram showing another embodiment of the vehicle power supplydevice according to the embodiment of the present invention;

FIG. 12 a diagram illustrating a method of supplying AC power to anelectric load; and

FIG. 13 a diagram showing a configuration to boost the voltage of thepower storage element device according to the embodiment of the presentinvention.

MODE TO CARRY OUT THE INVENTION Embodiment

Hereinafter, embodiments of the vehicle power supply device of thepresent invention will be described with reference to Figs. FIG. 2 is abasic embodiment of the present invention. A vehicle power supply device1 includes power storage elements (1 a to 40 d) constituting a secondarybattery charged by a power generation means (not shown) mechanicallyconnected to a drive mechanism mounted on the vehicle and traveling byan engine and a motor. The vehicle power supply device 1 includesswitching means (S1 a to S40 b), control means 200, leakage detectionmeans 100, and cutoff means 500, 501. The vehicle power supply device isconnected to electric load 300 which is operated by 12V, and one end onthe negative potential side is electrically connected to the vehiclebody. The vehicle power supply device 1 is connected to the high voltageload device 400 via the wire harnesses W1 and W2, and supplies theelectric power of the high voltage power storage elements 1 a to 40 d tothe high voltage load device 400.

In FIG. 2 , the power storage elements (3 b to 39 d), the switchingmeans (S3 b to S39 a) connected to the power storage elements, and theparts where the switching means and the control means 200 are connectedare omitted.

The power generation means is driven by an engine (not shown) in orderto supply the electric power required for the vehicle electricalcomponents. The power generation means is configured to regenerate thekinetic energy at the time of deceleration via the drive mechanism atthe time of deceleration of the vehicle and charge the power storageelement (1 a to 40 d).

Each node of the power storage element (1 a to 40 d) is, for example, alithium ion battery having a charging voltage of 3V. All the nodes ofthe power storage element (1 a to 40 d) are connected in series. A highvoltage power supply with a total of 480 V is formed, where 40 is amultiple N with respect to the required voltage of 12 V of the electricload 300. The high voltage power supply powers the electric drivecontrol system. The electric drive control system is composed of anin-vehicle motor, an inverter (not shown), etc. The high voltage powersupply acts to assist the driving torque of the engine. As a result,when the vehicle is power running, the energy regenerated duringdeceleration can be reused for traveling, so that it is possible toimprove the traveling fuel efficiency of the vehicle.

In the power storage elements (1 a to 40 d), the nodes 1 a to 1 d areconfigured as the first group node, the nodes 2 a to 2 d are configuredas the second group node, and the nodes 3 a to 3 d are configured as thethird group node. Then, the nodes 40 a to 40 d are configured as the40th group node. Switching means S1 a to S40 b are connected to bothends of each group node.

The total number of nodes of the power storage elements (1 a to 40 d) isN×n=160 in total by multiplying the multiple N=40 by the number n=4 ineach group node. In the claims, group nodes may simply be referred to asnodes.

Here, the total voltage of the power storage elements in series in eachof the first to 40th group nodes is 3V×4=12V.

As shown in FIG. 2 , the control means 200 controls the ON/OFF state ofthe switching means (Sla to S40 b) and the ON/OFF state of the cutoffmeans 500, 501.

As shown in FIG. 3 , the control means 200 turns on the switching means(S1 a, S2 a) and connects the electric load 300 and the first group nodeof the power storage element for [Ton] time. At this time, the switchingmeans other than the switching means (S1 a, S2 a) are turned off. Theswitching means S2 a is connected to the positive electrode side of thefirst group node, and the switching means S1 a is connected to thenegative electrode side of the first group node. Therefore, a DC voltageof 12 V is applied to the electric load 300 for [Ton] time.

Next, the control means 200 keeps all the above-mentioned switchingmeans (Sla to S40 b) OFF during the period [Td] shown in FIG. 3 . Thereason why the period [Td] is provided is that, for example, when theswitching means S1 a and the switching means S1 b are turned on at thesame time, an excessive current flows in the closed circuit. The closedcircuit is formed by the switching means S1 a, the switching means S1 b,and the nodes (1 a, 1 b, 1 c, 1 d) of the power storage element. This isbecause the switching means may be damaged or the charging power of eachpower storage element may be wasted.

It is assumed that, for example, a known MOSFET is adopted as theswitching means (Sla to S40 b). It is known that when a signal forcontrolling ON/OFF of each switching means is transmitted from thecontrol means 200, a time delay occurs until the switching means (S1 ato S40 b) actually respond. Therefore, the control means 200 requires asufficient waiting time [Td] from turning off the desired switchingmeans to turning on the other switching means. This [Td] is called deadtime. In the case of a general MOSFET, the dead time needs to be severaltens of nsec to several nsec.

As described above, the control means 200 turns on the switching means(S1 a, S2 a) for the first group node of the power storage elementduring [Ton], and connects the first group node to the electric load300. As a result, the required voltage of 12V is supplied to theelectric load 300. Subsequently, for the second group node, the secondgroup node is connected to the electric load 300 during [Ton] via theswitching means (Sib, S3 a). For the third group node, the third groupnode is connected to the electrical load 300 during [Ton] via theswitching means (S2 b, S4 a). Finally, for the 40th group node, the 40thgroup node is connected to the electrical load 300 during [Ton] via theswitching means (S39 b, S40 b). In this way, [T] shown in FIG. 3 isrepeated as one cycle, and the supply of 12 V DC power to the electricload 300 is continued. The charge/discharge state of each of the firstto 40th power storage element group nodes can be kept substantiallyuniform.

Next, FIGS. 2 and 4 will be referred to, and the operation of theleakage detecting means 100 will be explained.

The leakage detecting means 100 is connected to both ends of the powerstorage element (1 a to 40 d) via the terminal T102 and the terminalT101, and is grounded to the vehicle body via the terminal T103. Here,the earth leakage detecting means compares the current flowing betweenthe terminal T101 and the grounding terminal T103 with the currentflowing between the terminal T102 and the grounding terminal T103. Theearth leakage detecting means is configured to output the larger currentas an earth leakage detecting value from the terminal T100 to thecontrol means 200.

During the period when all of the switching means (Sla to S40 b) areOFF, the terminal T101 and the terminal T102 are floating with respectto the vehicle body, so the leakage detection value is OA. However, whenthe human body touches the positive electrode side of the power storageelement 40 d, that is, the T101 side, a leakage current is detectedbetween the terminal T102 and the ground terminal T103. This is becausethe resistance value of the human body is about 5 KΩ.

Therefore, as shown in FIG. 4 , the leakage detection means 100 has aleakage detection value [ILeak] of OA in the dead time period [Td1]. Inthe dead time period [Td1], the switching means S1 a and S2 a are turnedoff, and all the switching means including the switching means S1 a andS2 a are turned off. However, in the dead time period [Td2], the leakagedetection value [ILeak] in the leakage detection means 100 becomeslarger than OA. In the dead time period [Td2], when the human bodytouches the high voltage portion while the switching means S1 b and S3 aare ON, all the switching means including the switching means S1 b andS3 a are turned OFF.

The control means 200 inputs the leakage detection value [ILeak] to theterminal T200 of the control means 200 via the terminal T100 of theleakage detection means 100. When the control means 200 detects that the[ILeak] is equal to or higher than the predetermined value [ILth], thecontrol means 200 turns off the cutoff means 500 and the cutoff means501 during the [Toff] period, as shown in FIG. 4 , The time [Toff] isset to infinity, and after that, the cutoff means 500, 501 may remainoff.

Alternatively, as shown in FIG. 4 , the [Toff] is set to, for example,about 0.5 seconds, and the cutoff means 500 and 501 may be turned onagain.

If the leakage detection value [ILeek] of the leakage detection means100 in the dead time period [Tdn] exceeds [ILth] when the cutoff means500 and 501 are turned on again, it is determined that the human body isstill in contact with the high voltage circuit. Then, as shown by thebroken line showing the action of the cutoff means 500 and 501 in FIG. 4, the cutoff means 500 and 501 are turned off again to repeat on and off

When the cutoff means 500 and 501 are turned on again, if the leakagedetection value [ILeek] of the leakage detection means 100 in the deadtime period [Tdn] is less than [ILth], it is determined that the humanbody is not in contact with the high voltage circuit. As shown by thesolid line showing the operation of the cutoff means 500 and 501 in FIG.4 , the cutoff means 500 and 501 hold the on state and restart thesupply of electric power to the high voltage load device 400.

Since the high voltage power supply supplied to the outside from thepower storage elements 1 a to 40 d is cut off by the cutoff means 500and 501, the high voltage current does not flow through the human bodyand electric shock can be prevented. By surrounding the vehicle powersupply device 1 with a housing (not shown), it is possible to prevent ahuman body from touching the inside of the vehicle power supply device 1and receiving an electric shock.

Next, the power generation means (not shown) limits the charging voltageof the power storage element. The power generation means limits thecharging voltage so that the voltage in which the entire node of thepower storage element (1 a to 40 d) is connected in series becomes apredetermined maximum value.

On the other hand, the current consumption of the electric load 300 isnot constant, and may change significantly in a short time depending onthe operating state of the driver, for example, as in the case ofelectric power steering. In this case, if the switching means S1 a toS40 b are controlled by the control means 200 and the first group nodeto the 40th group node of the power storage element are switched atequal intervals, a difference may occur in the charging state of eachgroup node.

However, the control means 200 monitors the voltage of each group nodeof the power storage element via the terminals (T201, T202, T203 toT239, T240) shown in FIG. 5 . The control means 200 preferentiallyconnects the high voltage group node to the electric load 300. Then, thecontrol means 200 prevents the low voltage group node from beingconnected to the electric load 300. The control means 200 selectivelyswitches the storage element group (group node) to be discharged. As aresult, the charging state of each power storage element group (groupnode) can be kept substantially uniform.

As another embodiment, as shown in FIG. 6 , the control means 200monitors the voltage of each group node of the power storage element viathe terminals T (201, T202, T203 to T239, T240) shown in FIG. 5 . Thecontrol means 200 sets a long period during which the switching means isON for the high voltage group node. The control means 200 sets a shortperiod during which the switching means is turned ON for the low voltagegroup node. In this way, (Ton1 to Ton40) can be individually calculatedand controlled from the charge amount of the power storage element group(group node) and the current value flowing through the electric load300. As a result, each power storage element group (group node) ismaintained in a substantially uniform charging state.

As described above, as an action of the leakage detecting means 100, thepresence or absence of electric shock due to the contact of the humanbody with the high voltage portion during the period [Ton] is detected.The period [Ton] is a period in which any two of the switching means S1a to S40 b shown in FIG. 4 are ON. The detection is performed dependingon whether or not the leakage detection value of the leakage detectionmeans 100 in the dead time period [Td] at the moment when any of the twoON switching means is turned OFF is [ILth] or more and the cutoff means500,801 are turned OFF. Therefore, the maximum time for the electricshock current to actually flow to the human body is [Ton].

However, it is necessary that the electric shock current determined bythe voltage value of the high voltage power supply by the power storageelements 1 a to 40 d and the resistance value of the human body and thehuman body reaction expected from the duration thereof are within therange that is harmless to the human body. The duration is determined bythe [Ton] time. Generally, when the current value is 30 mA and theelectric shock time is 0.1 sec or less, it is said that there is nofatal human reaction.

That is, it is said that the maximum value of the product of theelectric shock current and the electric shock time is 0.003 amperesseconds in order to suppress the reaction to a safe human body.

Therefore, in this embodiment, it is assumed that the maximum electricshock current is 100 mA from the voltage value of the high voltage powersupply of 480 V and the human body resistance of 5 KΩ. From thisassumption, the electric shock time without harm to the human body iscalculated to be 0.03 sec or less. Therefore, the maximum value of theperiod [Ton] during which any two of the switching means Sla to S40 bare ON is set to 0.001 sec, which is a small value with sufficientmargin.

In a system equipped with the vehicle's high voltage power supply, notonly when the human body touches the high-voltage circuit part, but alsoa temporary leakage current may flow. The temporary leakage current iscaused by a leak of a mounted electronic component, a malfunction of aninsulating portion, vibration during traveling, or the like. In such acase, if the power supply from the high voltage power source to the highvoltage load device 400 is completely stopped by the action of thecontrol means 200, the function of each part may be lost while thevehicle is running, which may be dangerous.

Therefore, according to the embodiment, as mentioned above, in thecontrol means 200, when the leakage detection value [ILeak] of theleakage detection means 100 is equal to or higher than the predeterminedcurrent value [ILth], the cutoff means 500,501 are turned OFF. Thisstate is maintained for 0.5 seconds or longer. After that, the cutoffmeans 500,501 repeat the operation of turning ON.

As a result, even if a temporary leakage current occurs due to a failureof each part of the power supply device of the vehicle body, the powersupply from the high voltage power supply to the high voltage loaddevice 400 is resumed. The vehicle function can be restored, and drivingsafety can be maintained. Further, the state in which the cutoff means500,501 are OFF is set to 0.5 seconds or longer. As a result, theleakage current is not caused by the failure of the vehicle, and evenwhen the electric shock of the human body is actually caused, the fataleffect on the human body can be eliminated.

Here, when the leakage detection value [ILeak] of the leakage detectionmeans 100 is equal to or higher than the predetermined current value[ILth], the control means 200 keeps the cutoff means 500,501 OFF for 0.5seconds or longer. After that, the switching means repeats the operationof turning ON the cutoff means 500,501. At this time, the energizationtime [Ton] after restarting the operation is shortened in inverseproportion to the voltage value of the high voltage power supply by thepower storage elements 1 a to 40 d. Alternatively, it is desirable thatthe energization time [Ton] is shortened in inverse proportion to theleakage current value detected by the leakage detection means 100. As aresult, if the leakage is not caused by the vehicle but is an electricshock of the human body, the higher the voltage of the high voltagepower supply, the shorter the energization time to the human body.And/or, the larger the electric shock current of the human body, theshorter the energization time to the human body. It is more secure.

Next, in the vehicle power supply device 1 according to the embodimentof the present invention, the control means 200 switches the switchingmeans (Sla to S40 b) and switches each group node of the power storageelement (1 a to 40 d). This switching cycle will be described withreference to FIG. 10 .

It is assumed that the control means 200 switches each group node in thecycle [T] to supply a predetermined low voltage power supply to theelectric load 300. Further, it is assumed that the power generationmeans (not shown) is constantly charging so that the total voltage ofthe power storage elements (1 a to 40 d) connected in series becomes apredetermined value.

Here, as a group node of the power storage element selected by thecontrol means 200, for example, the first group node shown in FIG. 10can be given as an example. During the ON period of the first groupnode, the current flowing through the electric load 300 causes the firstgroup node to be in a discharged state and the charging voltage drops.At the same time, since the charging current is supplied from the powergeneration means so that the total voltage of all the power storageelements 1 a to 40 d becomes constant, the voltage changes in theincreasing direction in the group node not selected. The differencebetween the maximum voltage and the minimum voltage at the specificgroup node at this time is the so-called charge/discharge depth. As thewidth of the charge/discharge depth increases, the life of the powerstorage element decreases.

However, in order to suppress the human body reaction at the time of theabove-mentioned human body electric shock, the time [Ton] is shortened.Similarly, from the viewpoint of the life of the power storage element,the time [Ton] in which the power storage element group (group node) isselectively connected to the electric load 300 by the control means 200is shortened. At the same time, it can be seen that the control cycle[T] that goes around the selection of all the power storage elementgroups (group nodes) should be shortened.

However, as shown in FIG. 8 , in the ON transition process of eachswitching means, the current [I] increases as the voltage [V] across theswitching means decreases with the ON operation when the switching meansis in the open state. At this time, in this embodiment, switching lossoccurs in the switching means S1 a to S40 b. The loss I×V at this timewhen the switching means is in the open state is as follows. Forexample, if the voltage of each group node of the power storage elementis 12V and the current of the electric load 300 is 200 A, a peak loss of12×½×200×½=600 W occurs. Further, this switching loss also occurs in theOFF transition process of the switching means.

In addition, since the switching loss occurs during the dead time [Td],the average value of the switching loss with respect to the controlcycle [T] of the control means 200 is [Td/T]. As described above, thereis a problem that the switching loss becomes excessive by shortening thecontrol cycle [T].

Further, according to the present embodiment, the voltage [VL] appliedto the electric load 300 during the dead time [Td] period shown in FIG.3 becomes 0V during the period when all the switching means (Sla to S40b) are OFF. Therefore, since the power supplied to the electric load 300is momentarily interrupted, there is a problem that the low voltagevehicle electric load is momentarily stopped.

Therefore, as shown in FIG. 7 , the capacitor 310 is arranged inparallel with the electric load 300. As a result, the voltage charged inthe capacitor 310 continues to be supplied to the electric load 300.From this, the voltage [VL] does not drop to 0V, and can be limited to aslight voltage drop from the peak voltage as shown by the broken line[VLa] shown in FIG. 3 . The amount of voltage drop in this case isdetermined by the current flowing through the electric load 300, thecapacity of the capacitor 310, and the dead time [Td]. When the deadtime [Td] and the current flowing through the electric load 300 arefixed, the larger the capacity of the capacitor 310, the smaller theamount of decrease in [VLa] can be.

The amount of drop in [VLa] is determined by the capacity of thecapacitor 310, the dead time [Td], and the current value flowing throughthe electric load 300. Therefore, by adjusting the capacity of thecapacitor 310 and shortening the dead time [Td], the amount of drop ofthe [VLa] can be reduced. Needless to say this.

Therefore, it is possible to prevent a momentary interruption of thevoltage supplied to the electric load 300. Further, in the process inwhich any of the switching means (Sla to S40 b) transitions to the ONstate, the total voltage of the power storage elements connected inseries is 12V, and the voltage of the capacitor 310 is approximately12V. The total voltage of the power storage elements connected in seriesof 12V is a value at the group node of the power storage elements towhich any switching means is turned ON and connected. From this, thevoltage across the switching means can be set to approximately 0V whenthe switching means is in the open state. As shown in FIG. 9 , theswitching loss in this case is such that the loss I×V becomes theminimum because the current I increases while the voltage V remainsapproximately 0V.

In other words, the voltage of one group node of the power storageelement is output as the voltage supplied to the electric load 300. Itis utilized that the capacitor 310 holds the voltage of the group node.If the voltage of each group node is the same, the voltage of each groupnode when switching all the group nodes and the voltage of the electricload 300 (capacitor 310) are the same. The operation of the switchingmeans is so-called [ZVS] (known zero volt switching), and theoreticallyno switching loss is generated.

According to this embodiment, since the switching loss is not generatedat the time of stepping down from the high voltage power supply to thelow voltage power supply, the heat loss generated by the switchingelement used for stepping down is extremely reduced. In the experimentsof the inventors, when a step-down device having an output of 2.5 kW wasmanufactured, the power conversion efficiency was 99.5%. The heat sinkis no longer required, which makes it possible to significantly reducethe system cost.

As described above, the control means 200 does not stop the power supplyto the electric load 300 due to the detection of the leakage currentcaused by the vehicle. At the same time, in order to avoid danger due toan electric shock current to the human body, when the leakage detectionvalue [ILeak] of the leakage detection means 100 is equal to or higherthan the predetermined current value [ILth], the cutoff means 500,501are all held OFF state. For example, hold for 0.5 seconds (predeterminedtime) or more. After that, the switching means repeats the operation ofturning ON the the cutoff means 500,501 again.

In this case, the power supply from the high voltage power supply to thehigh voltage load device 400 is stopped for 0.5 seconds. It ispreferable that the capacitor (not shown) has a sufficient capacitanceis placed in parallel so that the specified voltage can be supplied fromthe capacitor to the high voltage load device 400 even during the stopperiod.

Next, as another embodiment, as shown in FIG. 11 , capacitors (601, 602to 640) are connected at both ends of each power storage element group(group node) formed by connecting four nodes in series among the powerstorage elements 1 a to 40 d.

It is known that the power storage element has an equivalent seriesresistance value of several tens of mΩ as an internal resistance (notshown) when, for example, a lithium ion battery is adopted. Therefore,in the case of four power storage elements connected in series in onegroup node in the present embodiment, each group node of the powerstorage element has an internal resistance of about 100 mΩ.

As shown in FIG. 3 , the voltage [VL] of the electric load 300 riseswhen one of the switching means is turned ON after the dead time [Td] isterminated. At this time, the electric time constant of the risingportion is represented by the product of the capacitance of thecapacitor 310 and the above-mentioned internal resistance. Therefore,when the capacitor 310 is charged by the internal resistance of thepower storage element, the rising waveform [VLb] of [VL] has a largetime constant and the low voltage state continues for a long time.Further, since this is repeated in the period [T], it becomes a factorthat the average value of the voltage supplied to the electric load 300decreases. It is desirable that the time constant be as small aspossible.

Generally, the equivalent series resistance of a capacitor as acapacitance element is as small as several ma Therefore, if a capacitor(601, 602 to 640) is connected in parallel with each group node of thepower storage element as in the present embodiment, the internalresistance of the power storage element is apparently reduced. As shownin FIG. 3 , the rising waveform [VLc] of [VL] when the capacitor 310 ischarged by the internal resistance has a small time constant and the lowvoltage state becomes short. Since this is repeated in the period [T],the decrease in the average value of the voltage supplied to theelectric load 300 is small, and the accuracy of the voltage supplied tothe electric load 300 is improved.

Hereinafter, a method of outputting AC power for supplying to a deviceoperated by a commercial power source from a plurality of power storageelements connected in series to form a high voltage power source will bedescribed. FIG. 12 is referenced. Since the basic configuration issimilar to the above-described embodiment, the figure showing theconfiguration in this embodiment is omitted.

First, as the power storage element, 180 lithium ion batteries having acell voltage of 3V unit are connected in series, and the total voltageis set to 540V. Next, the 60 power storage elements are regarded as onegroup node, and the whole is divided into three group nodes (G1 to G3).The voltage of each group node is switched every 1 ms by the switchingmeans and supplied to the commercial power supply load. When 10 ms haselapsed, the selected group node is G1. Next, when G2 is selected andsupplied to the commercial power load, the switching means is operatedto connect to the commercial power load. The polarity of the powerstorage element group (group node) is reversed. Subsequently, whenswitching between G3 and G1 while maintaining the same polarity, andfinally when G3 is selected and connected in the next cycle in which G2is selected, the power storage element group (group node) of which thepolarity is reversed when connecting to the commercial power load again.

By repeating the above operation, a rectangular AC voltage of 50 Hz, ±90V can be applied to the commercial power supply load.

As described above, in the vehicle power supply device according to theembodiment of the present invention, the high voltage power supply isformed by connecting power storage elements in series. By selectivelyconnecting a predetermined power storage element group (group node) fromthe high voltage power source to a low voltage electric load, powerconversion from high voltage to low voltage can be performed. At thattime, by switching the power storage element group (group node) at highspeed, the charge/discharge depth of the power storage element isreduced and the life is improved. At the same time, the switching lossof the switching means for switching can be made substantially zero. Ithas an excellent feature that the weight and cost of the member requiredfor heat dissipation of the switching element can be significantlyimproved.

In addition, a dangerous human reaction can be suppressed even when thehuman body touches the high voltage power supply circuit portion withoutusing means such as an isolated DC-DC converter.

As another embodiment, as shown in FIG. 13 , by exchanging the powerstorage element and the electric load in the above-described embodiment,the voltage of the electric storage means can be boosted and supplied tothe electric load. This is a matter that can be easily conceived by aperson having ordinary knowledge in the technical field to which thepresent invention belongs. In the embodiment shown in FIG. 14 , acapacitor constitutes a node and by charging each node with the voltageof the power storage element, it is configured to take out the boostedpower from the capacitors connected in series.

INDUSTRIAL APPLICABILITY

In the embodiment of the present invention, only a limited configurationand operation are shown as examples. The number of power storageelements connected in series, the type of power storage element, theelement type and configuration of the switching means, the type of thecutoff means, the number of the cutoff means, location of the cutoffmeans and the operation timing of the control means can take any form.At the same time, it should be easily understood that various knowntechniques exist as the configuration of the leakage detecting means,and that various failure detecting means and a fail-safe function at thetime of failure may be added.

DESCRIPTION OF NUMERICAL REFERENCES

-   1 a to 1 d power storage element (node)-   S1 a to S40 b switching means-   100 Leakage detection means-   200 control means-   300 electrical load-   400 high voltage load device-   500, 501 cutoff means

1. A power supply device for a vehicle, comprising: an electric loadthat operates at a predetermined low voltage; a high-voltage powersupply that provides a high-voltage DC power supply by connecting inseries a plurality of power storage elements constituting nodes thatsupply said predetermined low voltage; a high-voltage load deviceconnected to the high-voltage power supply via a wire harness; aplurality of switch means provided corresponding to said nodes thatsupply the predetermined low voltage to the electric load; a controlmeans, wherein the control means supplies a voltage by turning on one ofthe switch means for supplying the voltage from at least one node andturning off the other switch means for supplying the voltage from theother nodes, and after setting a dead time period to turn off all theswitch means once, by sequentially repeating turning on a next one ofthe switch means of a next node that supplies the voltage next andturning off the other switch means that supply the voltage from theother nodes so that the voltage is supplied from all the storageelements; a cutoff means for cutting off an electric circuit between thehigh-voltage power supply and the high-voltage load device; and aleakage detection means that detects a leakage current between thehigh-voltage power supply and a ground potential and sends a signal tosaid control means, wherein the control means determines the signaltransmitted from the leakage detection means during the dead time periodwhen the plurality of switching means are all off, and when the leakagecurrent is equal to or higher than a predetermined current, the cutoffmeans are kept off for a predetermined period of time.
 2. The powersupply device for the vehicle according to claim 1, wherein in saidhigh-voltage power supply, (n (n: natural number)×N (N: natural number))of said power storage elements constituting the nodes, in which n piecesof the nodes make up the predetermined low voltage, are connected inseries and a DC power source having a high voltage N times higher thanthe predetermined low voltage can be obtained.
 3. The power supplydevice for the vehicle according to claim 1, wherein said control meanscontrols the switch means so as to periodically change a plurality ofselected nodes.
 4. The power supply device for the vehicle according toclaim 3, wherein said control means determines a node to be selected sothat charge/discharge states of the plurality of power storage elementsbecome substantially uniform.
 5. The power supply device for the vehicleaccording to claim 3, wherein said control means determines a selectiveholding time of each node so that charge/discharge states of theplurality of power storage elements become substantially uniform.
 6. Thepower supply device for the vehicle according to claim 1, wherein a timefor connecting any of said nodes to said electric load by said switchmeans is set so that a time during which the leakage current flows fromthe high voltage power supply to a human body is less than a time duringwhich an electric shock accident is caused in the human body.
 7. Thepower supply device for the vehicle according to claim 6, wherein saidtime for connecting any of said nodes to said electric load by saidswitch means is set so as to be a time which is inversely proportionalto a voltage value of the high voltage power supply, or a time which isinversely proportional to a current value detected by the leakagedetecting means.
 8. The power supply device for the vehicle according toclaim 1, wherein said control means fixes the cutoff means to an offstate when a leakage detection value of said leakage detection means isequal to or higher than a predetermined current value.
 9. The powersupply device for the vehicle according to claim 1, wherein when aleakage detection value of the leakage detection means is equal to orhigher than a predetermined current value, said control means holds astate in which the cutoff means are off for a predetermined time andsubsequently repeats an operation in which the cutoff means are on. 10.The power supply device for the vehicle according to claim 1, whereinsaid control means controls said switching means so that a product of aperiod in which each node and the electric load are connected and aleakage detection value of the leakage detection means is 0.003amperes×1 second or less.
 11. The power supply device for the vehicleaccording to claim 1, wherein said control means sets a cycle forswitching a node selected by said switching means to be a predeterminedvalue or less so that a magnitude of a charge/discharge depth in eachnode of the power storage element is equal to or less than apredetermined value.
 12. The power supply device for the vehicleaccording to claim 1, wherein a capacitor is connected in parallel withthe electric load.
 13. The power supply device for the vehicle accordingto claim 12, wherein said dead time period or a capacitance value of thecapacitor is set so that a voltage drop width applied to the electricload during the dead time period is not more than a predetermined value.14. The power supply device for the vehicle according to claim 12,wherein the capacitor is arranged in parallel with each node of saidpower storage element.
 15. The power supply device for the vehicleaccording to claim 1, wherein from each node of the high-voltage powersource that provides said high-voltage DC power supply by connecting inseries said power storage elements, an AC power is supplied to theelectric load by alternately reversing a polarity with a high potentialside and a low potential side at predetermined periods when the electricload is connected by the switching means.